I admit I have never personally dealt with Mitsu intake butterflies but it's just two different runner lengths, right? one low RPM runner, one high RPM runner? Can't you just remove the butterflies, hammer a plug into each of the low RPM runners and suffer a couple fewer pounds of torque at low RPM? I know turning those big tires you need every pound of twist you can get but not if it means a risk of engine destruction.

Is there an intake manifold from like 3000GT's or something that doesn't have the dual runner length, where you could extend the throttle body out a little to bring torque peak down a few RPM?